This study investigates the interaction between 4.0 GHz microwave radiation and bovine coronavirus (BCoV). Previous work by the authors at 5.6 GHz demonstrated mild (~74%) but statistically significant reductions in virus survival, attributed to a combination of thermal as well as non-thermal effects, such as Structure-Resonant Energy Transfer (SRET). This research aims to expand the frequency dataset to better elucidate the roles of thermal and non-thermal effects in radio frequency (RF)-induced viral inactivation. These experiments were performed in a waveguide containing a flowing aerosol stream and were limited to a single RF waveform: ∼2 μs square envelope, 4.0 GHz, 4.8 kHz repetition rate. Aerosol streams were exposed to RF electric field amplitudes in the range of 41.5 ± 5.2 kV/m. Under laminar flow conditions, 80% of the total collected aerosol stream spends 1.0 s or less in the RF exposure region. Analysis via TCID50 assays revealed no statistically significant reduction in virus survival compared to controls, nor significant changes in data variance or standard deviation. Results align with prior observations that higher frequencies (~7-8 GHz) produce more pronounced inactivation effects, while lower frequencies exhibit reduced efficacy. The findings underscore the frequency dependence of microwave inactivation mechanisms and highlight the need for further studies at higher frequencies. Bioelectromagnetics. 00:00-00, 2025. © 2025 Bioelectromagnetics Society.

The recent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic had a tremendous impact on human life and global economics, motivating the invention of technology that can limit the spread of the virus from human to human in public areas. One candidate for such a purpose is radio frequency (RF) radiation, which was previously suggested to have a significant impact on viral integrity at exposure levels considered non-damaging to humans. However, these publications provided a limited explanation of the mechanism of action resulting in viral inactivation during RF exposure. One hypothesis was that structure resonance energy transfer (SRET) was occurring between the incident RF waves and the viral particle, which is highly dependent on the incident electric field strength. In this paper, we report exposures of bovine coronavirus (BCoV) to high peak power microwave (HPPM) pulses to validate the dependence of viral rupture on peak electric field as a critical parameter driving SRET. We tested 0.1-1.5 MW, 2 µs pulsed exposures of viral-containing buffer at 2.8, 5.6, 8.5, and 9.3 GHz up to 100,000 pulses and found no evidence of clinically significant E-field dependent decreases in viral infectivity. The findings reported in this manuscript do not support the hypothesis that SRET is a dominant mechanism behind RF-induced viral inactivation. Bioelectromagnetics. 00:00-00, 2025. © 2025 Published 2025. This article is a U.S. Government work and is in the public domain in the USA.

The natural vibrational frequencies of biological particles encode critical information about their structures and properties. The natural vibrational frequencies have been explored for early detection and inactivation of viruses. The resonant frequency-based biophysical methods present an interesting alternative to traditional vaccine and drug treatment against the spread and infection of pathogenic viruses. However, measuring natural vibrational frequencies of a single virion in a biological environment is challenging. Assigning structural features to measured spectra is even more difficult. We have simulated the dynamic motion of SARS-CoV-2 spike protein using all-atom molecular dynamics simulation. A resonance frequency at 7.3-7.4 GHz has been identified. The finding provides a molecular-level theoretical basis for attributing the experimentally observed SARS-CoV-2 microwave absorption peak at ~ 7.5 GHz to the intrinsic vibration of the spike protein, which is different from the previously proposed viral shell-core dipole model.

Previous research has shown that virus infectivity can be dramatically reduced by radio frequency exposure in the gigahertz (GHz) frequency range. Given the worldwide SARS‐CoV‐2 pandemic, which has caused over 1 million deaths and has had a profound global economic impact, there is a need for a noninvasive technology that can reduce the transmission of virus among humans. RF is a potential wide area‐of‐effect viral decontamination technology that could be used in hospital rooms where patients are expelling virus, in grocery and convenience stores where local populations mix, and in first responder settings where rapid medical response spans many potentially infected locations within hours. In this study, we used bovine coronavirus (BCoV) as a surrogate of SARS‐CoV‐2 and exposed it to high peak power microwave (HPPM) pulses at four narrowband frequencies: 2.8, 5.6, 8.5, and 9.3 GHz. Exposures consisted of 2 µs pulses delivered at 500 Hz, with pulse counts varied by decades between 1 and 10,000. The peak field intensities (i.e. the instantaneous power density of each pulse) ranged between 0.6 and 6.5 MW/m 2 , depending on the microwave frequency. The HPPM exposures were delivered to plastic coverslips containing BCoV dried on the surface. Hemagglutination (HA) and cytopathic effect analyses were performed 6 days after inoculation of host cells to assess viral infectivity. No change in viral infectivity was seen with increasing dose (pulse number) across the tested frequencies. Under all conditions tested, exposure did not reduce infectivity more than 1.0 log 10. For the conditions studied, high peak power pulsed RF exposures in the 2–10 GHz range appear ineffective as a virucidal approach for hard surface decontamination. © 2023 Bioelectromagnetics Society.

Experimental results from a study investigating the inactivation of bioaerosols containing Bovine Coronavirus (BCov) under repetitively pulsed radio frequency (RF) electromagnetic exposure will be presented. These experiments were performed in a waveguide containing a flowing aerosol stream and were limited to the use of a single RF waveform: ~2 μs square envelope, 5.6 GHz, 4.8 kHz repetition rate. Aerosol streams were exposed to pulsed RF electric field amplitudes in the range of 41.9 +/- 6.2 kV/m. Compared to the results of the control (no-RF) experiments, RF waveform exposure results in a 74% reduction in mean survival rate of the aerosolized BCov. RF exposure was also demonstrated to have a substantial impact on the variance of the experimental results, with the RF exposure data showing an 800% increase over the control results. Experimental results will then be compared to those from an analytic electromagnetic-heating inactivation model for aerosolized pathogens.

Inactivation of influenza A virus by radiofrequency (RF) energy exposure at levels near Institute of Electrical and Electronics Engineers (IEEE) safety thresholds has been reported. The authors hypothesized that this inactivation was through a structure-resonant energy transfer mechanism. If this hypothesis is confirmed, such a technology could be used to prevent transmission of virus in occupied public spaces where RF irradiation of surfaces could be performed at scale. The present study aims to both replicate and expand the previous work by investigating the neutralization of bovine coronavirus (BCoV), a surrogate of SARS-CoV-2, by RF radiation in 6-12 GHz range. Results showed an appreciable reduction in BCoV infectivity (up to 77%) due to RF exposure to certain frequencies, but failed to generate enough reduction to be considered clinically significant.

Emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its current worldwide spread have caused a pandemic of acute respiratory disease COVID-19. The virus can result in mild to severe, and even to fatal respiratory illness in humans, threatening human health and public safety. The spike (S) protein on the surface of viral membrane is responsible for viral entry into host cells. The discovery of methods to inactivate the entry of SARS-CoV-2 through disruption of the S protein binding to its cognate receptor on the host cell is an active research area. To explore other prevention strategies against the quick spread of the virus and its mutants, non-equilibrium molecular dynamics simulations have been employed to explore the possibility of manipulating the structure–activity of the SARS-CoV-2 spike glycoprotein by applying electric fields (EFs) in both the protein axial directions and in the direction perpendicular to the protein axis. We have found out the application of EFs perpendicular to the protein axis is most effective in denaturing the HR2 domain which plays critical role in viral-host membrane fusion. This finding suggests that varying irradiation angles may be an important consideration in developing EF based non-invasive technologies to inactivate the virus.

Images taken with an intensified CCD camera show the dynamics during filament guided discharge events. The images reveal that filament initiated corona plays a role in the presented results. Furthermore, the images show the formation of leaders, propagating and eventually bridging the gap between the high voltage (HV) electrodes. Analysis of the images and comparison to oscilloscope traces of voltage and current dynamics reveal the origin of the delay between the filament and HV discharge and allows for a probability of discharge analysis.

One application of ultrashort pulse filamentation is the coupling of external electric fields to filament plasmas and guiding of high-voltage discharges. However, the full physics of the guiding mechanism is still in question. Several models have been presented and explanations have been suggested to capture the full physics of the discharge event. For the first time, measurements of the electric field dynamics between two electrodes during filament-guided discharges are presented here, to the best of our knowledge. The electric field dynamics show an exponential growth region, a plateau, followed by a sharp drop off coinciding with the discharge event. We believe these results will ultimately answer the questions regarding the guiding mechanism. (C) 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)

We present an experimental study on beam combining techniques with multiple vertical external cavity surface emitting lasers (VECSELs) using volume Bragg gratings (VBGs). The specially designed holographic gratings introduce frequency specific feedback for the near infrared wavelength VECSELs to achieve both spectral linewidth narrowing and beam combination effects. For coherent addition, we obtained >3W output power with 8% slope efficiency in a coherent power scaling cavity scheme. In the multiplexed VBGs (MVBGs) wavelength beam combining compound cavity scheme, we measured >6W combined output with nearly 100% combining efficiency. Both beam combining/power scaling schemes produced spectrally narrowed and near diffraction limited outputs.

We report the observation of forward-propagating UV stimulated emission in atmospheric nitrogen pumped, at a standoff distance of 2.6 m, by an energetic laser pulse at a wavelength of 1053 nm and with the duration in the picosecond range. The generated optical gain at 337 nm is seeded by third harmonic of the pump beam. This demonstration is an important step towards the development of techniques for standoff optical sensing in the atmosphere.

We present an experimental study on active coherent combining of five Yb (Ytterbium)-doped fiber laser amplifiers that employs multiplexed volume Bragg gratings (MVBGs), reporting a combining efficiency of 82% and near-diffraction limited beam quality at a combined input power of 380 W, and 70% combining efficiency with equal beam quality at 670 W input power.

We densify dilute plasma in femtosecond laser filaments by heating it with energetic 200 picosecond-long laser pulses. Differently from the case of nanosecond heating, the densified plasma channels, under certain conditions, remain smooth and continuous.

In this research, we present the first MPI-CUDA implementation of Finite-Difference Time-Domain (FDTD) discretization of Maxwell's equations in dispersive media that uses the MPI API to assign each CPU node its share of the computational domain and GPUs to their corresponding CPU threads. By taking advantage of the CUDA programming model, we present a unique implementation of the FDTD scheme that exploits the memory hierarchy of GPUs, including the global, texture, and shared memory. This enables us to tackle problems that are otherwise computationally prohibitive. Practical results will be presented along with a measure of speedup factors achieved when using multiple GPU processors.

We present new insights into laser filament coupling to a high AC electric field strength of 100kV/m. Previous studies showed a short delay time for filament coupling. Our observations indicate a large time delay between the plasma and the discharge of the high field strength.

Highly efficient, stable, and scalable passive coherent beam combining of fiber lasers using multiplexed volume Bragg gratings is presented. We report combining efficiency of >;90% for two channels and demonstrate channel scalability to four channels.

Terahertz spectrometers and imaging systems are currently being evaluated as biomedical tools for skin burn assessment. These systems show promise, but due to their size and weight, they have restricted portability, and are impractical for military and battlefield settings where space is limited. In this study, we developed and tested the performance of a compact, light, and portable THz time-domain spectroscopy (THz-TDS) device. Optical properties were collected with this system from 0.1 to 1.6 THz for water, ethanol, and several ex vivo porcine tissues (muscle, adipose, skin). For all samples tested, we found that the index of refraction (n) decreases with frequency, while the absorption coefficient (μ(a)) increases with frequency. Muscle, adipose, and frozen/thawed skin samples exhibited comparable n values ranging between 2.5 and 2.0, whereas the n values for freshly harvested skin were roughly 40% lower. Additionally, we found that the freshly harvested samples exhibited higher μ(a) values than the frozen/thawed skin samples. Overall, for all liquids and tissues tested, we found that our system measured optical property values that were consistent with those reported in the literature. These results suggest that our compact THz spectrometer performed comparable to its larger counterparts, and therefore may be a useful and practical tool for skin health assessment.

Finite-difference time-domain (FDTD) methods are widely used to model the propagation of electromagnetic radiation in biological tissues. High-performance central processing units (CPUs) can execute FDTD simulations for complex problems using 3-D geometries and heterogeneous tissue material properties. However, when FDTD simulations are employed at terahertz (THz) frequencies excessively long processing times are required to account for finer resolution voxels and larger computational modeling domains. In this study, we developed and tested the performance of 2-D and 3-D FDTD thermal propagation code executed on a graphics processing unit (GPU) device, which was coded using an extension of the C language referred to as CUDA. In order to examine the speedup provided by GPUs, we compared the performance (speed, accuracy) for simulations executed on a GPU (Tesla C2050), a high-performance CPU (Intel Xeon 5504), and supercomputer. Simulations were conducted to model the propagation and thermal deposition of THz radiation in biological materials for several in vitro and in vivo THz exposure scenarios. For both the 2-D and 3-D in vitro simulations, we found that the GPU performed 100 times faster than runs executed on a CPU, and maintained comparable accuracy to that provided by the supercomputer. For the in vivo tissue damage studies, we found that the GPU executed simulations 87x times faster than the CPU. Interestingly, for all exposure duration tested, the CPU, GPU, and supercomputer provided comparable predictions for tissue damage thresholds (ED50). Overall, these results suggest that GPUs can provide performance comparable to a supercomputer and at speeds significantly faster than those possible with a CPU. Therefore, GPUs are an affordable tool for conducting accurate and fast simulations for computationally intensive modeling problems.